What the plans actually differ on
Every plan translates all 79 languages. The difference is not what Voxis understands — it is what you hear.
Paid plans stream the translated voice from the cloud engine, so all 79 languages are spoken aloud.
The free tier speaks on your machine, not in the cloud — and which voices your machine has is what the two free columns above differ on. Either way the cloud still translates all 79: a language without a voice arrives as live subtitles instead of speech. Nothing breaks; you read it rather than hear it.
In the Windows and Linux app Voxis ships its own open neural voices and downloads the one you need on first use. Those exist for 35 of the 79; the other 44 are subtitles.
In the browser extension there is nowhere to run those voices, so it uses the ones your browser already has. On Windows that is 18 of the 79 in Chrome and 16 in Edge — the two Edge is missing are Hindi and Indonesian. The exact list depends on your browser and on the speech voices installed in your operating system, so a machine with extra language packs may speak more than the table shows. The extension tells you before you press Start when the language you picked has no voice on your machine.